Most of the reasons fall in the three categories I mentioned before.
(1) this is not limited to watches. One can celebrate a milestone in many ways, buying a car, taking a trip abroad etc.
(2) (3) (4) (5) and (7) fall in the category of watches as art
(6) is minority and only a thing in the past couple of years, except for “watches as art” which was always a thing
I mentioned it in order to set a different context to the OP’s question. When one wants to wear mechanical watches, but also benefit from the features of smartwatches there really is a struggle to find a way. Obviously this doesn’t matter in the grand scheme of life, but hey, this is an AW forum not “how to solve world hunger”